High abrasion-resistant coating compositions find use in a wide variety of coatings applications. Because such compositions form coatings which tend to increase the hardness and abrasion resistance of substrates, they are desirable for use in protecting the surfaces of said substrates. For example, high abrasion resistant coating compositions are used in the manufacture of transparent articles, including building windows, aircraft windows, eyeglasses, and lenses, to prevent dulling, pitting and scratching of the surfaces thereon. Additionally, high abrasion resistant coating compositions are used to help metal substrates, such as those made from aluminum, maintain physical and structural qualities.
A useful class of such high abrasion resistant coating compositions are those derived via sol-gel procedures. Traditionally, such coating compositions have been produced by reacting one or more inorganic alkoxysilane compounds to form a curable composition comprising a network of siloxane bonded (—Si—O—Si—) moieties.
More recently, alkoxysilated amine compounds have been used in conjunction with inorganic compounds to form high abrasion resistant coating compositions via sol-gel procedures. For example, U.S. Pat. Nos. 5,316,855 and 5,371,261, issued to Wilkes et al., disclose the use of alkoxysilylated organic compounds containing urea (—NH—C(O)—NH—) and/or urethane (—NH—C(O)—O—) bonds in the preparation of sol-gel derived curable compositions. Such organic compositions are reacted with metal alkoxide or semi-metal alkoxide compounds to form curable compositions.
The present inventors have discovered that the use of organic compounds containing urea (—NH—C(O)—NH—) and/or urethane (—NH—C(O)—O—) bonds in curable compositions is disadvantageous for several reasons. For example, one disadvantage is that organic compounds containing urea and urethane moieties are susceptible to hydrolysis. The hydrolysis of such compounds in the water-alcohol borne sol-gel compositions leads to “dangling” side groups, which lowers the abrasion resistance of the resulting coatings. In addition, the hydrolysis raises the pH of such compositions which, in turn, shortens gelling time and reduces the shelf life of the compositions.
Recognizing these and other drawbacks of the prior art, the present inventors have perceived a need for new, stable alkoxysilated organic compounds for use in a variety of applications, especially sol-gel coatings applications. These and other objects are achieved by the present invention as described below.